micro "mud" flaps spotted
 

what are they

aero? mini mud flaps?

just like dams in front of the tires started appearing a few years ago and now all cars seem to have them, i recently spotted somethig interesting in several cars

it's a small tab on the rear wheel arc behind the wheel... it looks mostely like a mini mud flap, but it's location and size makes it a little suspect

http://i77.photobucket.com/albums/j5...ghway/comp.jpg

even the new mercedes C class coupe has it, as does the new ford fiesta and the Citroen C3 and C4

they're basically very little bulges that sit high on the wheel arch, sometimes molded as a part of the plastic bumper or as part of the inner wheel well liner.

so their place and size make me wonder if they're really there to stop rocks or whatever but perhaps they have something to do with watter spray, wich can be really annoying.

any ideas on what they are for?

Very interesting!

I can't find any hi-res pictures of that area through Google, so I'll have to take a closer look next time I see one in a parking lot. It's too bad that I usually don't have a camera with me (In the spirit of waste reduction I still have a stone age cell phone).
My first uneducated guess would be that maybe that bulge somehow controls turbulence in the wheelwell. Sort of like a 'virtual' wheelskirt.
But it may just as well control water spray. These two ideas aren't even mutually exclusive.

On the Fiesta and the new Merc C Coupe there's definitely something there.
See :
http://www.autoguide.com/gallery/d/9...ro-Spec-16.jpg
http://www.autoblog.nl/gallery/Merce...acelift_12.jpg

On the C4, it may be sloppy photoshopping or workmanship mounting the bumper - I can't find a pic illustrating it a bit better.

My car has them and it's a 1996 chrysler, perhaps it's just for looks? Aesthetic purposes maybe.

There is a Ford Fester in our parking area, its got them on. I wonder if its usually the first bit to scrape the wall when some one parallel parks into it...

Otherwise, I'll stay posted until someone comes up with a proper answer...

Get a smart phone. Reduce your overall energy consumption. Betcha never heardsomeone advertising the green aspect of these wretched contraptions, eh?

I'll err on the water sparay side. Happy to be proven wrong.

From Ford's website:

"The subcompact Ford Fiesta is available with a Super Fuel Economy (SFE) package that enables the car to achieve 40 mpg highway. This package features cruise control, low rolling-resistance tires and several additions to enhance vehicle aerodynamics, such as underbody shields, side air deflectors and lower grille blockers."

Maybe the "side air deflectors"? Kind of a vortex generator?

Here is a screen grab of a Youtube video of a Fiesta. Looks like micro vg's on the top of the mirror. Interesting.

http://i54.tinypic.com/2cqflsn.jpg

to help fill the hole left by the mirrors maybe?? i wonder what that looks like in a wind tunnel test. i would expect them to be just like the ones the Evo MR has above the rear window, proof of concept, but not enough to actually make a difference

micros
 

Short answer,I don't know.
If I had to guess,I'd be inclined to think that the fins trigger separation and create a vorticity which helps negate back-soiling of dirty rainwater from the fender well onto rear light lenses during inclement weather.

BMW did something similar years ago on some models, with small semi-circular bulges in the gap between the mirror and the side windows.

I don't recall the car types, but I've seen more of these on mirrors.
The mirrors on the Volvo V50/S40 have a small boattail ;)

So apparently, some manufacturers are taking measures to cut down the drag from the mirrors.

measures
 

They're also going after wind noise.

The "dimples" used on the BMW's were solely there to reduce wind whistle between the mirror and the pillar.
By eliminating the noise there was probably some aero benefit as well but BMW never claimed any.

Peter.

a lot of aerodynamic modifications are indeed made to reduce wind noise and watter flows. and therefore not nessesary reduce drag. i can't imagine the original bulges being there for noise reduction.

what i find odd is that recently a lot of independant manifacturers seem to have come up with a simalar solution... but to what problem?... wheel have changed fairly little since cars first came out. sure they contribute to drag but how does a little bulge all of the sudden solves that...

it will be nice to see one on a rainy day to see if that explains anything...

Never underestimate the power of aerodynamic marketing.

Yeah. The focus groups liked the fender accent look, but loved the efficiency claim.

This isn't marketing. The bulge or flap isn't noticeable... and the flap, if you do notice it, is ugly.

To prevent stones being tossed upwards by tire, they are quite close to edge of wheel arch these days?

I just spotted something similar to these micro "mud" flaps... on my car! These point inward and are in the front wheelwell (none in the rear). I admit that the similarity may just be a coincidence.
Looking towards the rear:

Looking towards the front:

not sure if these are the same but they might be related,i don't suppose they're somehow helping to keep the inner liner in place but i suspect it might have something to do with watter, either spray when you're moving or drips when your stationary.

a lof of complonents on a car have tiny bumps, dimples or holes, to allos watter to drip from them in a certain location and not collect in another where it might cause rust.

Perhaps it's worth checking after driving on a rainy cay if there's any difference in dirt deposit around these tabs or if you can see watter dripping from them.

if you ever wash the car with a hose might also be a good idea to observe what happens when you point it at this area

They are for homologation to IIRC - some countries get all narky about expsed tires and when viewed from above you can't have a certain & of tyre exposed on ANY wheel/tire combo in the range so these little lips are built into every variant as for economy of numbers. th'ye somethimes on the front fenders too. alway wear the fender where the fender starts to taper toward the centre line.

do you have any source to back up that claim? not that something like that would be impossible but it seems unlikely to me that all of the sudden several independant manifacturers find their stock fenders to narrow for all their tire options (i have yet to see a version of these cars that have oem tires extend past the fenders ). i know that local law here forbids tires that extend past the fenders,(although the actual text might be vague enough to allow such "cheats"). i'll have another look at them with what you said in mind.

Sorry, what part are you talking about? The silver tabs inside the fenderwell?

I thought that we had been looking at / talking about something that protruded outward from the fenderwell, not something that poked inward.

Yep. When I noticed them I thought about this thread since they are 'tabs in wheelwells', but I admit that this may be where the similarities end.

Ah, okay, thank you. The ones you pictured are, I think just to help in fabrication and to hold the fender liners in place.

I recently spoke to a senior engineer who worked on the Astra GTC and he confirmed this; they are for EU homologation concerning coverage of the tyres, not for aerodynamics or road spray control.

I realize you may be trying to be funny, but that sort of comment - whether it be directed at Europeans, gays or anyone else - is inappropriate and should have no place in this forum.

Frankly, as a southerner myself, I'm embarrassed that it was posted here.

This is what I was thinking too.

:confused:
Could someone explain?

Laws state you can't have the wheels/tires poke out completely outside the fenders. Further, the tires can't poke past any part of the body over a certain amount. They never had a problem like this before because no one cared much about wheel fitment. Now having the wheels flush to the fender is all the rage (see, "hellaflush", "stance movement") and OEM's want to get in on it. Problem is, the kind of fitment car enthusiasts get is not legal to produce from the factory. Therefore they put these tabs on to "cover" the wheels when viewing at a certain angle, so the tires technically aren't protruding from the fenders.

You can see the tires stick out farther than the bottom of the bumper. The bumper tapers in but the tire is vertical. The tire "tucks" under the fender at the top and "pokes" out at the bottom.

The OEM's can't legally produce something that takes this characteristic too far. Putting those tabs on visually "covers" the tire so they can push it out farther with a lower offset wheel.
http://carblueprints.info/blueprints...-door-2008.gif

Here you can see it in real life:
http://image.motortrend.com/f/103730...+rear_view.jpg

The wheel/tire fitment goal is something like this: low, flush
http://speedmotiv.com/posts/816/images/focus_02.jpg

Tabs let them cheat the laws into having lower offset wheels stock. I will bet it's mostly designers like me b****ing and whining to have better wheel fitment, and the lawyers coming back telling them it's not possible. Then the designers come up with some little cheat that allows both of them to get what they want: a cool looking car they can legally sell.

The idea that the little flaps are reg cheaters is interesting.

I have to wonder how far it can be pushed by dedigners/builders
and accepted by buyers/drivers.

In the C1 class canoe, the hull has to be a certain minimum
width across at the waterline. But one of the factors in theoretical
hull speed is width. Enter this within the rules, but very difficult to
keep upright, result:

http://www.bearmountainboats.com/gallery/C1/C-1_01.jpg

FWIW, "tracking" or ability to keep to straight line is excellent. :D

Most likely some part of the directive states "no part of the tyre may be visible from above" or " no part of the tyre may stick out from the body work".

These flaps are positioned where the bodywork toes in vertically and horizontally.
The result is that when seen in plan view, the extreme edges of the tyres could (barely) be visible - so they need covering.